Annals of Biological Research
Abstract
Author(s): Hossein Soleimani1*, Hassan Ahmadi1 and Gholamreza Zehtabian2
Drought is both a hazard and a disaster; a hazard because it is an accident of unpredictable occurrence, part of the
naturally variable climate system; disaster because it corresponds to the failure of the precipitation regime, causing
the disruption of the water supply to the natural and agricultural ecosystems as well as to other human activities.
Drought definitions are many and often are equated with specific drought impacts on economic activities,
ecosystems, and society and water management issues. The objective of this study is to provide a comparative
spatial analysis by using IDW methods as one of important geospatial methods and temporal variability of drought
index in Taleghan with the view to identifying trends and onset of drought. It will quantify the relative effectiveness
of SPI, DI and CZI and precipitation data as drought indices in the Taleghan region as a unique and highly
productive basin. Taleghan is also a semi-arid region with a 41-year rainfall average of around 520 mm. Most
rainfalls are in winter and spring. Geographic information system (GIS), GS+, Excel and DIP are good tools for
analyzing spatial location, interaction, structure and processes. In this research the SPI, DI and CZI has been used
as reference indices for the identification of drought events. Data-set is collected from 8 climatology station within
the watershed from 1967 to 2008. After testing and if needed normalizing the data, it was entered in Excel and after
being saved as a text, it was transformed to the DIP software to calculate the SPI, DI and CZI. In the second stage,
we used data in GS+ to assess the spatial variability of SPI, DI and CZI as Geostatic calculations. We analyzed the
spatial relationship of SPI, DI and CZI with IDW by using GS+ only for yearly data. To increase the insurance, we
used cross validation to make better decision in choosing the best method for mapping. To determine the degree of
accuracy of maps, the cross validation between the three ways was analyzed. The R2 factor was used as an
important indicator to assess their accuracy. In the meanwhile, t-student test in 1% level was calculated to
distinguish the significances.
